Method and apparatus for treating liquid-containing material based on organic waste products

ABSTRACT

Liquid containing organic waste material and chemicals are continually introduced into the upper part of a vertical, cylindical treatment chamber. While sinking through the chamber, the material is beaten by fast rotating treating elements which also mix the material. The treating elements also move in axial direction to free vapors and gases from the material. Vapors and gases are removed from the top of the chamber.

The invention relates to a method and apparatus for treatingliquid-containing materials based on organic waste products,particularly sludge from sewage plants. The treatment is carried outwith the particular aim to make the material suitable as a fertiliser orsoil improvement medium.

BACKGROUND OF THE INVENTION

Prior treatment plants are based on batchwise feeding of the materialinto a treatment chamber into which chemicals are added. The chemicaladditives cause reactions in the material resulting in heat generationand evaporation of liquid regulation of the pH value and increase ofnitrogen in the final product. Then heat is added to the thus chemicallytreated mass to evaporate liquid and to achieve a desired percentage ofsolid matter in the final product.

This prior technique suffers from several drawbacks and deficiencies.Thus, batchwise treatment is not an effective approach. Also, therelatively high temperatures as used (about 425° C.) result indestruction of humic acid and other substances important to soilimprovement.

Furthermore, when the reaction processes take place within the mass,gasification of liquid is hampered and the results of the reactionprocesses generally lowered. Using external heat for gasification/dryingand granulation after reaction treatment the temperature should besufficiently low to avoid loss of the material substances that arevaluable to soil improvement. Various low temperature technologyprocesses may be adapted to this process. However, the properties of thematerial emanating from the reaction treatment would be of greatimportance, also for the result of this process.

The prior art also includes continuous processes for treatingliquid-containing materials such as sewage sludge, as disclosed in U.S.Pat. No. 4,038,180 and EP-A-0 356 781. However, such prior processessuffer from the same drawbacks as discussed above in connection withbatchwise material feeding, and in addition they tend to be lessefficient owing to the slow throughput needed to ensure a sufficientsludge dwell time for the required reactions and drying to take place.

The main object of the invention is to provide an approach that permitsa continuous process, and that does not require external heating of thesludge to effect the necessary evaporation, while keeping thetemperature sufficiently low to avoid loss of any of the substances inthe material that are valuable for improving soil.

According to the invention this object is achieved through a method andan apparatus as defined in the accompanying patent claims.

SUMMARY OF THE INVENTION

The reaction processes are activated when the material is being directlybeaten by the rotating beating means as it falls through the verticaltreatment chamber. Liquid and air are beaten out of the pores of theparticles in the solid mass, and compact, free particles are formedunder conditions promoting degasification. Also, the liberated liquidpresents a relatively large surface promoting evaporation anddegasification together with a cooling effect serving to keep thetemperature sufficiently low, while the heat developed by the chemicalreactions is sufficient to produce the desired evaporation. In a suchcontinuous process free liquid surrounding the particles willeffectively absorb heat energy supplied. Also, with compact particles,one is far more free in choosing granulating or pelletising equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail below, with referenceto the drawings in which:

FIG. 1 is an elevational view of an apparatus according to the inventionsuitable for treating e.g. sewage sludge,

FIGS. 2 and 3 are successive, enlarged longitudinal sectional views ofthe apparatus according to the invention, and

FIGS. 4, 5 and 6 are elevational, plane and crossectional viewsrespectively of details of a treating element.

DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to FIG. 1, the apparatus 1 according to the inventiongenerally comprises a material treatment chamber 2 having an upper gaswithdrawal portion 3, a material feed assembly 4, a material dischargeassembly 5 and two drive assemblies 6, 7.

With reference to FIGS. 2 and 3 treatment chamber 2 generally consistsof a vertically oriented cylindrical housing 10 which, in the embodimentshown, is conveniently made up of several sections. An inlet 11 providedwith a feed screw 12 for feeding material to be treated is disposed inthe upper part of the chamber and inlets 14 in the form of verticallydirected nozzles 15 for adding chemicals are disposed at the level of orbelow the material inlet 11. Above inlets 11, 14 the treatment chamber 2merges into the gas withdrawal portion 3 the top of which is defined byan end wall 16, the bottom of the chamber 2 being defined by an open endor outlet 17.

A tubular body 18 is centrally and rotatably disposed in chamber 2.Rotationally fast with but axially slideably surrounding the tubularbody 18 is a shorter tubular sleeve 19 carrying a plurality, e.g.eleven, treating means 20.

Internally of the tubular body I 8 there is a shaft 21 which isrotatably journalled in the tubular body independently of the rotationof the tubular body. Shaft 21 extends upwardly through a lop wall 22 ofhousing 10, where it is connected to an overhead drive unit 6, such asincluding an electric motor of a type adapted to impart to shaft 21 aperiodical, intermittent rotary motion in opposite directions. A pulley25 disposed between housing top wall 22 and chamber end wall 16 is keyedat 26 to an upper end of tubular sleeve 19 and driven through to acertain transmission via not shown pulleys by a drive pulley 27 locatedin a housing lateral section 28 also carrying the drive motor 7 fordriving the drive pulley 27.

In the embodiment of the invention as shown and described herein therotational support of the tubular body 18 in the cylinder housing isprovided by an upper bearing assembly 30 and a lower bearing 32. In theexample as shown the upper bearing assembly is made up of two ballbearings 36, 37 spaced by spacer rings and mounted with their outerraceway rings in the upper end wall 16 of the withdrawal portion upperend wall 16. A seal 38 disposed at the end of a dependent portion 40 ofthe end wall seals with the outer periphery of tubular body 18.

The bottom bearing 32 is shown as an axial/radial roller bearing theouter raceway ring of which is locked in the lower end of tubular body18 and the inner raceway ring of which is locked against a shoulder on acylindrical pedestal 42 internally disposed at the bottom of the tubularbody, with a spacing therebetween, and rigidly secured by a centrallocking screw 44 and locking disk 45 to a spiderlike housing 10 bottompiece 46 that also defines a lower end of treatment chamber 2. A seal 48internally disposed in bottom piece 46 seals with the exterior oftubular body 18.

The rotational support of shaft 21 in tubular body 18 comprises an upperbearing assembly 50, an intermediate bearing 51 and a lower bearing 52.The upper bearing assembly 50 consists, like the tubular body upper ringassembly 30, of two ball bearings 56, 57 which are spaced by spacerrings and the outer raceway rings of which are locked, via further upperspacer rings, between an internal shoulder 60 of tubular body 18 and atop locking disk 61 also axially locking pulley 25 and upper tubularbody bearings 36, 37 inner raceway rings to the tubular body. The innerraceway rings of axial bearings 56, 57 are locked via an upper spacerring between a collar 64 and a locking ring 65 of shaft 21.

The intermediate bearing 51 is locked in a conventional manner by meansof locking ring 66 and locking disk 68 respectively, to shaft 21 andtubular body 18 respectively, while the bottom bearing 52 is locked,also in a conventional manner, to the shaft and tubular body by alocking ring 69 and end cover 70 respectively, the latter being providedwith a seal 71 sealing with a portion 72 extending therethrough.

A lower externally threaded extension 74 of shaft 21 co-operate with alongitudinal substantially cylindrical bushing nut 75 having an upperportion which, via bearings 76, 78, are connected to a carrier ring 90slideably disposed internally of the tubular body and rigidly secured totubular sleeve 19 by bolts 91 each extending through a respective one oftwo diametrically opposed, vertically extending slits 92 formed intubular body 18. In the shown example bolts 91 also extend through arespective treating means 20. A bushing 94 surrounds each bolt 91between tubular sleeve 19 and carrier ring 90.

A lower end portion of the threaded extension of the shaft depends intoa cylindrical bore 95 formed in the pedestal 42 and sized to receive,with a certain clearing, a lower portion of nut 75 in the bottomposition thereof as shown in FIG. 3. Shaft 21 has a bottom locating pin96 received in a mating recess in the bottom of the pedestal bore. Inthe upper part of the pedestal bore there is a locating lug 98 extendinginto a mating longitudinal groove 99 in the external periphery of thebushing nut, thus keeping the nut rotationally at rest during rotationof the shaft.

The tubular sleeve 19 is, as previously noted, axially slideable on theexterior of the tubular body 18, e.g. with a radial spacing of about 1.4mm. Seals 100 seal with the exterior of the tubular body.

When shaft 21 is periodically rotated in opposite directions, nut 75will move upwardly or downwardly on the shaft, depending on therotational direction of the shaft, thereby implying to the tubularsleeve, via carrier ring 90 and bolts 91, a corresponding axial motionup and down on the tubular body, with a length of stroke of e.g. 100 mm.

In FIG. 3 nut 75 with tubular sleeve 19 is, as previously noted, shownin a bottom position, while FIG. 2 shows tubular sleeve 19 in its topposition.

The treating means 20 mounted on the exterior of the tubular sleeve 19may have any shape suitable for their purpose, namely to forcefully hitor beat the sludge material during its sinking through the treatmentchamber 2, while simultaneously serving to effectively intermix thechemicals added in the chamber into the sludge material.

As best shown in FIGS. 4-6 the treating means 20 may consist of aplurality of generally U-shaped elements having two legs or <<teeth>>101 which, when the elements 20 is mounted on the tubular sleeve, extendradially outwardly toward the internal peripheral surface of thecylindrical housing with a small spacing therebetween, and anintermediate base portion 102 having mounting holes 103 for securing theelement to the tubular sleeve. Each element 20 may advantageously bemounted on a carrier ring 104 adapted to be threaded onto the tubularsleeve and secured to the latter by screws. The teeth 101 have agenerally flat impact surface 105, i.e. the front surface hitting thesludge material during operation of the apparatus according to theinvention. The treating elements 20 are evenly distributed downwardlyalong the periphery of the tubular sleeve 19, as shown in FIGS. 2 and 3.Preferably, the axial spacing between the elements 20 is somewhat lessthan the stroke of the nut assembly 75, so that their end positionsoverlap.

In order to provide for a dwell time of the material in the treatmentchamber 2 sufficient to allow the desired chemical reactions to takeplace in a complete manner, the treatment chamber 2 should have a lengthof about 2 meters below inlet 11.

The method according to the invention when using the above describedapparatus, is substantially as follows.

Having started the drive assemblies 6, 7 the material to be treated,such as sludge, is continuously fed into treatment chamber 2 throughinlet 11 by means of feed screw 12, while pressurised concentratedsulphuric or nitric acid is introduced through chemical inlet 14. Thesludge sinks by gravity down through the treatment chamber where theporous organic material is exposed to the beating action from therapidly rotating treating means 20 which also cause a strongly turbulentenvironment positively serving to intermix the inflowing acid into thematerial. A suitable rotational speed of tubular sleeve 19 with itstreating means is in the range of 1500 and 3000 rpm. Exhaust gases fromthe chemical reactions thus taking place will flow upwardly in treatmentchamber 2 and into the withdrawal portion 3 thence vented through aconduit 107 (FIG. 1) to a condenser, for example, the condensate ofwhich will be suitable for use as a liquid fertiliser. The frontsurfaces 105 of the treating means 20 will beat out liquid and airtrapped in pores in the solid contents of the material and thuseffectively separate the liquid from the solid matter, to permit thelatter to assume the shape of relatively compact particles, while theseparated liquid is liberated for effective evaporation under theinfluence of the heat generated by the chemical reactions, the vapoursand reaction exhaust gases ascending through the degasing portion.

The vertical overlapping travels of the rotating treating means 20enhance the mixing effect, while the outer end portions of the treatingteeth 101 serve as scrapers against the internal surface of thetreatment chamber 2, thus keeping the latter free of deposits. Thefrequency of the periodical vertical motion of the treating means 20 isdetermined in relation to the percentage of solid content of thematerial feed, about 3000 cycles per minute being suitable for aninitial solid matter content of about 30%.

Then, by means of the conveyor screw 106 of discharge assembly 5 viaadditional conveyor screw or other suitable means 108, the thusacid-treated material is carried into the inlet of a further treatmentapparatus 1 of the construction shown in FIGS. 1-3 and described above,in which the process is repeated, the only difference being that nowammonium is inserted through the chemical inlet 14 rather than acid. Ifdesired, additional additives to take part in the ammonium treatment areinserted through side inlets 109 in the conveyor screw 108 between thetwo treatment apparatuses 1--1, continuously proportioning the weight ofadditives relative to the mass being treated. The amount of addedammonium will normally be about 30% of the weight of acid used,resulting in a nitrogen content in the material of about 10%, and thesolid matter content will be raised to about 45%.

Factors of importance to the treatment process, such as temperature, phvalue, nitrogen content etc. in the sludge material, is measuredcontinuously or intermittently and are simply controlled by controllingthe speed of feed of the material and the amount of chemicals.

I claim:
 1. In a method for treating a liquid-containing organic wastematerial comprising the steps of: continuously feeding the material intoan upper inlet (11) of a substantially vertical, cylindrical treatmentchamber (2); adding treatment chemicals to the material through achemical inlet (14) on the chamber; mixing the materials and chemicals;heating the mixture to evaporate the liquid and degas the material so asto render the material into a higher solids content; and removing fromthe chamber evaporated liquid and gases; and wherein the mixing step iscarried out by a plurality of beaters (20) mounted on a tubular sleeve(19) which is axially slideable on an exterior of and rotatable about atubular body (18), said beaters (20) extending essentially to adjacentan inner cylindrical periphery of the chamber, whereby the sleeve (19)is simultaneously rotated about and reciprocated in an axial directionon the tubular body (18).
 2. The method of claim 1, wherein thetreatment chemicals include at least one acid, the acid and material arefed into the chamber, and the treated material is discharged from thechamber into an additional chamber in which ammonium is inserted.
 3. Themethod of claim 1, wherein the evaporated liquid and gases are condensedinto a liquid fertilizer.
 4. The method of claim 1, wherein the tubularsleeve is rotated at not more than 3,000 rpm.
 5. The method of claim 4,wherein the tubular sleeve is rotated at 1,500-3,000 rpm.
 6. The methodof claim 5, wherein the tubular sleeve is rotated at about 3,000 rpm. 7.The method of claim 1, wherein the material is caused to sink by gravitydown through the chamber (2) from an outlet (17) and is caused to passthrough said outlet into a conveyor (106) provided under the chamberwithout passing any essential constriction.
 8. The method of claim 2,wherein the material is conveyed towards said additional chamber bymeans of a conveyor.
 9. An apparatus for treating a liquid-containingorganic waste material comprising: a substantially vertical, cylindricaltreatment chamber (2); an upper material inlet (11) on the chamber; achemical inlet (14) on the chamber; a mixer disposed within the chamber;and a vent at an upper end of the chamber for venting gas from thechamber, and wherein the mixer comprises a plurality of beaters (20)mounted on a tubular sleeve (19) which is axially slideable on anexterior of and rotatable about a tubular body (18), said beaters (20)extending essentially to adjacent an inner cylindrical periphery of thechamber, such that the sleeve (19) simultaneously is rotatable about andreciprocal in an axially direction on tubular body (18).
 10. Theapparatus of claim 9, wherein the tubular sleeve (19) is rotationallyfixed on the tubular body (18).
 11. The apparatus of claim 10, whereinthe tubular body (18) is centrally located in the chamber.
 12. Theapparatus of claim 11, wherein the tubular member (18) coaxiallysurrounds and is operably connected to an independently rotatablesupport shaft (21).
 13. The apparatus of claim 12, wherein the shaft(21) has a threaded portion (74) cooperating with a nut (75) which isconnected to the tubular body (18).
 14. The apparatus of claim 13,wherein the connection to the tubular body (18) is by way of bolts (91)extending through vertical slits (92) formed in the tubular body (18).15. The apparatus of claim 9, wherein the beaters (20) have teeth (101)which extend radially outwardly from sleeve (19) and have asubstantially flat impact surface (105).